Aliasing artifacts in MRI (originating from Nyquist artifacts, or intra-scan motion induced phase errors, among others) greatly reduce the quality of clinical MRI data. For example, it is well known that the inconsistency of k-space trajectories corresponding to opposite frequency-encoding gradient polarities in echo-planar imaging (EPI) results in Nyquist artifacts. Traditional techniques often only correct for phase errors along the frequency-encoding direction (i.e., 1D correction), which may still leave significant residual artifacts, particularly for oblique-plane EPI or in the presence of cross-term eddy current. As compared with 1D correction, two-dimensional (2D) phase correction methods can be much more effective in suppressing Nyquist artifacts. However, existing 2D correction methods can require extra reference scans and/or may not be generally applicable to different imaging protocols. Furthermore, it is believed that EPI reconstruction with 2D phase correction is susceptible to amplification of errors in reference scans. In addition, the intra-scan motion induced image-domain phase errors in segmented diffusion-weighted imaging (e.g., segmented diffusion-weighted EPI; segmented diffusion-weighted spiral imaging; segmented diffusion fast-spin echo imaging among others) result in severe aliasing artifacts in the acquired data. Furthermore, the large scale motion may result in k-space phase errors in segmented MRI acquisition (e.g. segmented EPI; segmented spiral imaging other others), producing aliasing artifacts in reconstructed images.
Other MRI pulse sequences/image acquisition types, with or without parallel imaging paradigms, can also be susceptible to Nyquist and/or motion-induced artifacts, and/or other types of aliasing artifacts.